This project aims to investigate preschoolers' developing concept of intention. In particular, the proposed research examines children's appreciation of intention as a mental state that motivates, yet is distinct from, action. In addition to its significance for children's developing social competence, knowledge about mental states like intention is heavily implicated in other areas of development such as moral reasoning, language acquisition, metacognition, and academic achievement. Moreover, deficits in understanding others' mental states have been documented in individuals suffering from autism as well as in children with conduct disorder. Thus, it is of fundamental importance to investigate the nature and developmental course of children's understanding of mental states. Intentions, along with beliefs, desires, and other mental states, operate in a network to influence human behavior. Hence, children's understanding of intention will be examined in relation to their understanding of these other mental states. Specifically, Study 1I investigates preschoolers' ability to use information about beliefs and desires to differentiate two intentions for the same action. There are times in which one action may be compatible with multiple intentions, and the ability to identify the relevant intention is crucial for interpreting others' behavior. Study 2 examines whether children understand that one intention can give rise to different yet equally appropriate actions. This is the complementary aspect of understanding that one action may result from different intentions, and is also important for assessing children's developing concept of intention as a mental state that is distinct from the behavior it motivates. Finally, Study 3 investigates children's ability to use information about intentions in making moral judgments. The ability to draw accurate inferences about intentions is critical for making attributions of praise or blame. In all three studies, 3-, 4-, and 5-year-olds will hear pairs of stories in which two characters either perform the same action to fulfill different intentions (Studies 1I and 3) or perform different actions to fulfill the same intention (Study 2). Children will be asked to determine the characters' intentions on the basis of information about their beliefs and desires.